Sheet metal clamp



Dec. 5, 1944. l F, C, WALLACE 2,364,408

SHEET METAL CLAMP Filed April 9, 1943 7l-71437712557@ Monk CWaZZace, @y

Patented Dec. 5, 1944 SHEET METAL CLAMP Frank C. Wallace, Los Angeles,Calif., assignor to Herman H. Helbush, Los Angeles, Calii'.

Application April 9, 1943, Serial No. 482,413

3 Claims.

This invention relates to sheet metal clamps of the type commonly usedfor holding together superposed perforated sheets with the perforationsin alignment.

My invention has for one of its primary objects the provision of safetyfeatures for clamps of the type wherein a pair of clamping fingers orpinsare reciprocally mounted in a cylindric body for protraction andretraction relative thereto, the retraction 'being accomplished byarelatively strong 'spring normally urging the clamping pins intoretracted position relative to a spreader positioned therebetween. Whensuch a clamp is in work-clamping position, or even in idle position, theonly element preventing the spring from forcing the parts intodisassembly are the enlarged outer ends of the pins engaging the work orthe end of the clamp body, as the case may be. If the enlarged ends wearunduly or break off, the spring acts to propel the pins and body inopposite directions with considerable force with the result that notinfrequently serious injury results to workmen. By my invention Iprovide simple and effective means for safe-guarding against thisdanger.

Another object is the provision in such a clamp of an improved clamp pinconstruction and arrangement.

Another object is the provision of a clamp incorporating improved meansof assembly.

Still further advantages are inherent in my invention and how those asWell as the objects hereinabove pointed out are achieved will beapparent from the following detailed explanation of presently preferredembodiments, for which purposes I shall refer to the accompany drawingin which:

Fig. 1 is a longitudinal section showing parts in position occupied when'device is not in use;

Fig. 2 is a longitudinal section showing retaining pins protractedpreparatory to inserting in perforations;

Fig. 3 is a longitudinal section showing device in clamping position;

Fig. 4 is a section on line 4-4 of Fig, 1;

Fig. 5 is a section on line 5-5 of Fig. 1; and

Fig. 6 is a perspective of the spreader.

Referring now to the specic example of my invention illustrated in thedrawing, the numeral 5 denotes a cylindric body having an annular flange6 providing an undercut shoulder 1 for the reception of aclamp-operating tool, not shown. At the outer end of the bore of thebody there is a counter-bore 8 for the reception of an end wall or ringmember 9 having a central opening I0 therethrough, and a dished cap I Ihaving a central opening I 2 has its peripheral edge tting within thecounter-bore 8 against the end wall 9, both the end wall and cap beingheld in the body by peening the end of the body over the peripheral edgeof the cap.

The opposite or inner end of the body has a bore' I5 of relativelyreduced diameter whereby to provide a shoulder I6 which acts as a stopto limit outward movement of a thimble Il, which latter is reciprocallymounted in the body.

Mounted within the body and the thimble I provide a plunger comprising apair of retaining pins 20 whose inner ends project through a centralopening 2| in a cap 22 and are -bent over as shown at 23 to prevent thepins from 'being pulled out of the cap. The side walls 24 of the cap arebent over to provide a housing for the inner ends of the pins. By meansoi this cap the inner ends of the pins are held against lateralseparation.

The inner opposed faces of the pins abut each other to a point spacedinwardly of the body from the cap 22, at which point 20a they oisetoutwardlyto provide a space between the outer end portions of the pins.The outer ends of the pins project through the concentric holes I0, I2astride a T-shaped spreader, whose inner cross arm 25 is rotatablydisposed in the space provided between the end Wall 9 and cap AII andwhose central leg 25a projects through opening I2 in the cap I l betweenthe pins 20.

The outer end of each of the pins 2U has an enlargement 2b providing ashoulder 3B facing the outer end of the body.

A coil spring 32 bears at one end against end wall 9 and at its otherend against cap 22 within the thimble and thus normally urges theretaining pins 20 into retracted position and normally urges the thimbleoutwardly of the body.

To prevent escape of the thimble and its carried elements from the body,the thimble is vprovided with a peripheral flange 33 which engages theshoulder I6 when the retaining pins are in fully retracted position. Theouter, closed end o1 the thimble is spherical so that when engaged by arelatively flat clamp-operating tool only a minimum of fractionalresistance to rotation of the thimble and its carried pins relative tothe body is offered, such relative rotation being desirable to preventdamage to the retaining pins when they are engaged by a tight nt in aperforation in the work.

To assemble my improved clamp, the pins 20 are rst assembled in the cap22 and inserted in the thimble along with the spring. Then the thimbleand its carried pins and spring are inserted longitudinally of the bodybore, being inserted from the outer end, after which the wall 9 isapplied. Next the cap Ii is applied and held suiilciently separated fromwall 9 to insert the spreader. By then compressing the springsufficiently the outer end of the body is crimped over the peripheraledge of the cap Il. Another simple procedure for assembly is to firstinsert the thimble l1 into the body from the outer end, then insert thepins through the opening in the cap I l, then insert the spreader byplacing its cross arm in and against the dished surface of the cap andprojecting its central arm outwardly through the cap opening and betweenthe pins, then applying the ring 9 over the pins. Next, the cap orferrule 22 is applied, the inner ends 23 of the pins are bent over, andthe side wall 2l of the cap 22 is bent over the pins. assembly may beinserted in the body from the outer end thereof and secured in positionas by peening the outer end of the body.

To operate the clamp, it is placed in a clampoperating tool, forinstance of the character shown in United States Patent No. 2,296,439,and while the body is held stationary, the thimble with its carried pinsare forced inwardly of the body against the pressure of the spring toprotract the outer ends of the pins far enough beyond the outer end ofthe spreader leg 25a to be flexed together by engagement with the sidewalls of the perforations P when inserted in registering perforations Pin the sheets S to be clamped (see Fig. 2). Usually the diameter of thehole I2 through the cap and the diameter of the perforations P aresubstantially the same and each hole is of a diameter equal to thecombined thickness of the two pins and interposed spreader at a pointimmediately above the shoulders 30. Release of the tool pressure on thethimble permits the spring to retract the pins relative to the spreaderand body, thus causing the sheets S to be clamped resiliently betweenthe shoulders and the cap Il (see Fig. 3).

From the foregoing it Will be observed that any accidental escape of theouter ends of the pins through the openings 9 and I2--as will occur ifthe engaged ends become unduly worn or break oil-the thimble and bodyare prevented from completely separating by virtue of the annular flange33 on the thimble encountering the body shoulder I6.

Another important advantage of the structure described resides in thefacility and economy of providing for assembly.

I claim:

l. A sheet metal clamp, comprising, in combination,` a cylindric body,an end cap secured on the body in position closing the outer endthereof, said cap presenting an opening therethrough, a dished innerportion and an outer4 work-engaging portion, a plunger reciprocallymounted in the body, said plunger presenting a pair of work-engagingpins protractable and retractable through said opening, spreader meansThen this for separating the pins, including a T-shaped bar having itscross arm disposed in the dished portion of the cap and having itscentral arm projecting outwardly from the cap through said opening andbetween the pins to a point spaced outwardly from the outer surface ofthe cap, an inwardly disposed flange on the inner surface of the bodyadjacent its inner end, a. coil spring in the body around andretractively engaging the plunger and tool-operated means forprotracting the plunger against the pressure of said spring, comprisinga plunger-engaging member reciprocally mounted in and projecting fromthe inner end of the body for manual engagement, said member having arelatively increased diameter inner end portion engageable against saidflange when the plunger is in fully retracted position.

2. A sheet metal clamp, comprising, in combination, a cylindric body, anend cap mounted on the body in positionv closing the outer end thereof,said cap presenting an opening therethrough and a work-engaging outersurface, a plunger reciprocally mounted in the body, said plunger havinga Work-engaging member protractable and retractable through saidopening, a spreader member having a laterally projecting inner endportion disposed in the cap and an outer end portion projectingoutwardly through said opening in engagement with the work-engagingmember, an inwardly disposed flange on the inner surface of the bodyadjacent its inner end, a coil spring in the body around andretractively engaging the plunger and tool-operated means forprotracting the plunger against the pressure of said spring comprising aplungerengaging member reciprocally mounted in and projecting from theinner end of the body for manual engagement, said member having arelatively increased diameter inner end portion engageable against saidflange when the plunger is in fully retracted position.

3. A sheet metal clamp comprising a body presenting a longitudinal borehaving a reduced diameter inner end portion providing an inwardly facingshoulder, a ring in the outer end of the bore, a cup-shaped cap securedto the outer end of the body, said cap having an opening concentric withthe ring, a plunger reciprocally mounted in the bore for protraction andretraction through said ring and opening, a spreader having a laterallyprojecting inner end portion mounted between the capA and ring and anouter plungerengaging portion projecting outwardly through said opening,a coil spring in the body bearing at its outer end against the ring andbearing at its inner end against the plunger to normally urge theplunger retracted, and tool-operated means for protracting the plungeragainst the pressure of the spring, comprising a plungerengaging memberreciprocally mounted in and projecting from the inner end of the body,said member presenting a peripheral flange engageable against saidfirst-named shoulder whenvthe plunger is fully retracted.

FRANK C. WALLACE.

